Field of the Invention
The present invention generally relates to rotors supported by mechanical bearings, and more particularly to a method and apparatus for unloading the weight of the rotor from its bearings.
Discussion of the Background
Rotors, such as those used for storing rotational kinetic energy, have shafts along their axis of rotation that are typically supported by rolling bearings. Thus, for example, a vertically oriented rotor may have a lower rolling bearing and an upper rolling bearing. For such configurations, the lower bearing must usually be designed to support the weight of the rotor.
While the use of rolling bearings to support rotors is effective, the typical use of such bearings requires large bearings. Thus, for example rotors used for energy storage may have a weight in excess of 1,000 pounds. Roller bearings capable of supporting large weights are necessarily large and expensive. In addition, as is known in the field, ball bearing lifetime is limited by raceway fatigue, and scales inversely with the cubic power of the bearing load.
There exists a need for an apparatus and method that can reduce the axial load on the roller bearing supporting a rotor. The apparatus and method should be compatible with existing rotor designs and be easy to implement. The apparatus and method should also provide for longer bearing lifetimes.